Final answer:
CT colonography cannot biopsy or remove polyps, while a conventional colonoscopy allows for both identification and removal of precancerous growths.
Step-by-step explanation:
The chief disadvantage of CT colonography over conventional endoscopy is that it cannot biopsy or remove polyps. Although CT colonography, also known as virtual colonoscopy, is a less invasive procedure and can identify polyps and potentially cancerous lesions, it does not allow for their immediate removal. In contrast, a conventional colonoscopy is both diagnostic and therapeutic, as it enables the physician not only to identify precancerous polyps, but also to remove them during the same procedure, which can help prevent the polyps from becoming malignant.